Aircraft undercarriage



July 5, 1960 @.QRLOFF -ET'AL 2,943,819

. AIRCRAFT UNDERCARRIAGE Filed July 18. 1956 2 Sheets-Sheet 1 e f@ 'f Aff- /fy fig M11/f ff i@ fd gf INVENTORS GEORGE ORLorF RoBERT ROY .Br-mmm E. Couven KENNETH TJ. LANnoN www, (344, m www ATTO'R NYS July 5, 1960 G. oRLor-F ETAL AIRCRAFT UNDERCARRIAGE 2 Sheets-Sheet 2 Filed July 18, 1956 INVENTURS Gemme ORLoFF Ronan-r Rov .BERNARD E.Coo1 E`R KENNETH T P LAusnoN ATTOR NEYS AnzcRAFr ArJNnnRcAnuman George Orlo, Robert Roy, Bernard Edward Cooper, and

Kenneth Thomas Peers Langdon, Gloucester, England, assignors toBritish Messierl Limited, Gloucester, England, a British company j i Filed July 1s, 1956, ser. Nu.' 598,507 claims priority, application Great Britain July zo, 195s z claims. '(ol. 244-50) u 'I`Ihis invention comprises improvements in or relating to aircraft undercarriages. YMore particularly the invention relates to steerable undercarriages ofthe kind in which one or more landing wheels are mounted on a rotatable steering member or leg supported by a fixed element secured to the aircraft, the range of angular displacement of the leg being limited by stop means aud-the steering movementbeing effected Within said range by driving means operable from within the aircraft. `In this context the expression stop means is not limited to positive stops deliberately provided for arresting the angular movement but is also inclusive of vany bar to unlimited rotation of the leg which isinherent in the nature of thedriving connections to theleg.

It is known to employ such an undercarriage in which -t-he means for eifecting the steer-ing movements comprise an hydraulic jack controlled from Within the aircraft. It is an object of the present invention to provide a construction of the kinddescribed which is modified to render it more adaptable when used on an aircraft which is being towed on the ground.

The present invention comprises a steerable aircraft undercarriage of the kind described, wherein the stop means limiting the yangular movement of the leg are such as to be capable of being disconnected from the leg or otherwise rendered'inoperable, and means are provided for so disconnecting or rendering inoperable the stop means when the aircraft is to be moved on the ground other than under its own power.

The stop means limiting the -angular movement of the leg may occur in the, driving means for rotating the leg, and means may be provided for disconnecting the driving means and thereby also rendering the stop means inoperable on the leg, when the aircraft is to be moved on the ground other than under its own power. j

When a vehicle is used to tow the aircraft along the ground therefore, the angle of steering movement of -the undercarriage may be unlimited, Whereas when the aircraft is propelling itself over the ground it is limited to an angle within the range afforded by the stop means, which angle is chosen so as to be within safe limits..

One specific example of construction according to the invention Awill now be described with reference to theaccompanying drawings, of which:

Figure 1 is -a sectional side elevation of the steering `connection and disconnecting mechanism according to the invention; Y

v Figure 2. is a cross-sectional view along the lme 2--2 in Figure 1;

Figure 3 is a cross-sectional .'ew along the line `3--7-3 in vcross-section which is. non-rotatable, `being lixed with re- 2 spect to the airframe, and an inner relatively rotatable casing `112 also of annular crossfsection, which is sup-` ported partly within and coaxial with the outer casing by means ofsuitable bearings, one of which is shown at 113. Means for retaining the inner` casing therein in the` axial direction Vare provided but are not shown. The inner casing 112 extends from the' outer casing and at its extrernity carries the aircraft nose wheel, together .with shock-absorbing ,means not shown. A short distance away from the end of theA outer casing 111 the inner casing 112 is on its outer surface stepped at 114 toa slightly larger diameter part 115, and is :furtherA stepped at 116 to a still larger diameter part`117. This part is stepped down again at 118 to a diameter equivalent to that of part `115. Loosely mounted upon part 115 of the inner casing is an annular member 119'provided with a pair of forked flanges 120, 1 21 extending radially outwardly therefrom. As shown in Figure 1 a boss 122 is provided centrally on each ofth'ese anges 4and this is provided with a tapped hole .1,23 therethrough, the axis of this hole lying parallel with the axis of the inner and outer casings. A suitable bolt 124'is screwed into eachtapped hole and a spigot 125 on the end of'each bolt projects into a hole 126, one hole drilled in each of two diametrically opposed lugs.V 127 integral withV the external surface of the cylinder 128 of an hydraulic steering jack12j9. In this way a pivotal connection is provided'between the jack cyiinder and the fork flanges 120 and 121. The jack rod 13% is pivotally connected at 131 to a flange 132 projecting Vfrom the outer casing 111. Flange 120 is further provided writh bosses 133 and 134 disposed symmetrically on either side of the respective boss 122, such ,that they projectA from the ange. Broth bosses are provided with a drilled hole 135 and 13,6, theaxes of which are parallel to those of the tapped holes 123. As will be seen in -Figure 1, two connecting rods 137 and 138 of I crosssection and forked at both ends are each at one end re-Y spectively pivotally connected at bosses 133 and 134 .to u

the ange 120 by pins 139 and 140 which pass through -holes'135 and 136 and holes as at 141 in the fork ends. These pins are retained by Washers 142, 143 and split pins 144 and 145. The opposite forked end of each connecting rod is also provided with `drilled holes as at 146 andpins 147 and 148 are provided in these holes so as to of greater diameter.

support 4rollers 149 and 1,50 between each pair of forks. The axes of these pins are disposed in a plane parallel to the `axes of pins 139 and 140. Spacing washers 15.1 are provided on either side of each roller and the pins project from their respective connecting rods, being then provided with a washer as at 152, a second roller 153, 154 and a further washer 155', 156. Each pin assembly is retained with respect to its connecting rod by a castellated nut 157, 15S screwed onto a threaded extension 159, 160 of the respective pin and locked by means of split pin 161, 162. Rollers 149'and15il normally (i.e. during steering) both engage a collar member 163 which is secured by a key 16-4upon the inner casing 112 between the end of the outer casing 111 and the step 114, abutting againstv the step and the corresponding face of the annular member 119. Collar member 163 is provided with a peripheral projection 165 with which the rollers 149 and 150 are held in engagement by a coil spring 166 secured to, in convenient manner, and extending between, connecting rods 137 and 133. The peripheral projection is of V'greater diameter through an angle of about 190 than the remaining 170, and steps 167 and 168 down to the lesser diameter part are of part circular configuration, the radius thereof approximating to that of rollers 149 and 150 so that these rollers may seat against these steps. A small chamfer 169, 170 is provided where the steps merge into the part The end of the outer casing adjacent thecollar` member-,163 is provided, integral therewith, with two outwardly extending radial flanges 171, 172 each extending peripherally through an angle of approximately 90 and disposed symmetrically about the outer casing 111 such that the greater part ofY eachange is disposed Q` the. Sffrnsiaksid@ Qf e line ZZ (ses Figure 2.)- These flanges are provided with part-circumferential slots 1'73k and 174 having-1a width, and disposedina radial plane, such that the rollers 15,3, 154 may respectively roll therein. Atboth ends each slot diverges outwardly and ,isprovided with a semi-circular seating, Vas at 175, for therollers.v t Y The operation of this mechanism will; now be described.

f As. in the first erribodiment, when itis desired to steer the nose wheelfthexseryo valve means (not shown) associated `witlrthe s'teeringojack 412,9V are operated to 1direct lhydraulic tiuid to either `side olf the) jack piston to move v,theeey'flirrder 128` in'vthe desired direction. VSuch valve lmeans may be ofthefollQw-np type which automatically ,centralise `to the neutral position when the jack cylinder moves to its new position. Now it will vbe yappreciated Ithat the arrangement of the jack and its driving connecvtions to Athe rotary leg prevents the leg from rotating Ibeyond certain angular `limits for so long as the drive is yc onr led to the leg. These limits are however beyond the positions at which' the -rneans for disconnecting the drive ,eoire intooperation, so that when the legis subject to -a torque applied externally ofthe aircraft it is able to rotate ,as far `as these positions unhindered. Thesevis also another pairof limits imposed yon the leg rotation; these-are the angular limits to which the leg is able to turn when being rotated through the'driving connections under the control of the pilot. Since it is clear that to avoid un- .timely'disconnection of the, driving means, the leg when .being rotated under the pilotsl control must not reach as .far'round'asxthe positions at which disconnection takes place, this further pair of limits is well within the range otsaid positions. To fix said further pair of limits, a *cameupon the pilots controlmember (not shown) ,operates azmivcroswitch connected withy a limiting valve in the pres- ,surelline to the servo valve means controlling the jack, and lwhen the pilotscontrol is moved far enough in either direction to bring the leg round to the'limit to which it 4can b eallowed to Yrotate under these circumstances, the -cai-n and micro-switchco-operate to operate said limiting valve andV shut olfl the pressure supplyvmotivating the jack1 l Asbeforethelimits to which the leg turns when rotated by thejack under the pilots control are well within the range o ftheu positions at which disconnection of the drivingnconnections Afrom the jack takes place, although the leg can movebeyond said positions under an externally-appliedtorque,

:A'Letfus tassnmerthat the inner casing 112 is positioned angularly within the steering range, which may be of the ,order o f i35 from the straight ahead position. Operation of the steering jack 129` results in movement of the jack cylinder in one direction or the other so that the annular member 1 19 turns either in the .clockwise or anticlockwise direction by virtue of the pivotal connection between its anges 120, 121 and the cylinder 128. Consequently the connecting rods 137 and 138 and rollers 149V collar member '163 together with the inner casing 112 and lnose wheel are turned in either the clockwise or antinclockwise direction, -as the case may be.

As previously stated, when it is required to tow the :aircraftit is desirable that the nose wheel and inner casing 112.should be capable of free rotational movement so that aground 'manoeuvring is facilitated. Accordingly-a tow- 'ingarrn is at one end attached to a suitable projection '(not shown) on the rotatable inner casing 112. The nose whe'eband inner-casing may be rotated'by manualmovement of the towing arm, about the `axis of the nose wheel leg, against the fctional resistance in the hydraulic steering jack 129, the valve mechanism thereof being inthe neutral position, and against the frictional resistance between the type of the nose wheel and the ground. Assuming that this turning is in the clockwise direction as viewed in the drawings 'the step 167 on the collar member 163 is urged against roller 149 so that connecting rod 137, annular member 119 and connecting A'rod 138 also turn in a clockwise direction, the jack cylinder 128 therefore moving to the right in the drawings. Such turning is continued until each roller 153 and 154 moves outwardly -against the effort of coil spring 166 into one or other of the divergent end seatings 175 of its associated part-circumferential slot 173, 174. In this way rollers 149 and 150 ride out of the part-circular seatings formed by steps 167 and 168 over the chamfers 163, 170 into a position clear of the larger diameter part of the collar member 163, so that the collar member and nose wheel may be rotated freely inthe clockwise and the'anti-clockwis'e directions by the towing arm. In this' respect this 'constructin differs fromthe rst construction since once the steering jack cylinder Vis moved to the end'of its stroke andthe rollers aredisengagedifrom the collarmer'nber, only movement of lthecylinde'r in thejopposite direction under hydraulic power willre-engage the 'steeringlinkage Y. Figure 4 shows Vthe mechanism in the disconnected position. Y

` vvlf when the mechanism is in the normal steering'position-the towingoarm is vinstead moved so that the'collar jmember 163'moves in the anti-clockwise direction, release of the* rollers 149,and 150 fromthe collar member will loccur when the jack cylinder reaches the other end of its stroke and'when'the rollers 153 and 154 move outwardly into'the opposite'divergent end parts of thepart-circumfverential slotsY 173 and 174. Similarly the collar member and nose'wheel may then be rotated freely in the clockjwise and the anti-clockwise directions by the towing arm, but to re-engage thev steering linkage it is necessary to vhydraulically operate the jack.

4We claim:

l. .An aircraft undercarriage leg comprising a tixed member,v a driven member mounted for' rotation in said iixed member, rotator means connected between said tixed'and driven members for rotating said driven member relatively to said xed member, a Vpair of operative vconnectionsbetween said rotator means'and said driven member, each of which operative connections incorporates a first abutment and a second abutment cooperat- 'ing with-'said firstkv abutment, Aone of which abutments is connected' to said rotator means and the other of which Falbiltmen'tsis connected to said driven member, one of said pair of operative connections being provided for transmitting drive in'each 'direction of rotation of said ',drivenmember relatively to said fixed member, said leg being characterized in that each of said operative'connections comprises a detentA arm angularly movable'with respect to its' Vsecond abutment, in that its first abutment lis constituted by a roller rotatably carried by said detent arm and itsy second abutment is constituted by a' step, and inv that engaging and disengaging means are pro- 'vided'for vholding said roller and step positively in engagement and for positively moving said lroller and step 'out of'en'gagementin dependence upon the relative angular vpositions of said Xed and driven members, said engaging and disengaging means.comprising-a'cam'track lnonrotatably connected to 'said tixed member and al cam `follower connected to said detent arm toV moveit angularly. r

2. An aircraft undercarriage leg comprising a yfixe-d imember, a driven member mounted for rotation in said fixed member, rotator means connected between said --ixed and drivenV members for rotating-said driven mem- Vberrelatively Vtoxsaid fixed member, a pair of operative .'connections between said lrotator meansand said'driven member, (each of .which.operative .connections incorporates a irst abutment and a second abutment cooperating with said first abutment, one of which abutments is connected to said rotator means and the other of which abutments is connected to said driven member, one of said pair of operative connections being provided for transmitting drive in each direction of rotation of said driven member relatively to said ixed membensaid leg being characterized in that each of said operative connections comprises a detent arm angularly movable with respect to its second abutment, in that its rst abutment is' constituted by a roller rotatably carried by said detent arm and its second abutment is constituted by a step, and in that means are provided for holding said roller and step positively in engagementand for `positively moving said roller and step out of engagement in dependence upon the relative angular positions of said fixed and driven members, said rotatable member having connected thereto a camrxed against rotation relative to said rotatable member, said cam having a first cam surface part thereof concentric with said rotatable member and a second cam surface part also concentric with said rotatable member Vand of larger radius than `said first part, and connecting cam surface parts connecting said rst cam surface part with said second cam surface part, each said step being formed by one of said connecting cam surface parts, and in which each said detent arm is pivoted at `one end thereof to said rotator means and carries said roller, which cooperates with said cam at its other end. Y

References Cited in the file of this patent FOREIGN PATENTS i 993,036 France July 1s, 1951 

